Style of fluid flow and deformation in and around an ancient out-of-sequence thrust: An example from the Nobeoka Tectonic Line in the Shimanto accretionary complex, Southwest Japan

Hideki Mukoyoshi, Tetsuro Hirono, Hidetoshi Hara, Kotaro Sekine, Noriyoshi Tsuchiya, Arito Sakaguchi, Wonn Soh

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

To understand the characteristics of deformation of an out-of-sequence thrust (OST) and the style of fluid flow along it, we investigated the Nobeoka Tectonic Line, which has been interpreted as a deep OST (7-9 km), in the Shimanto accretionary complex, Southwest Japan. The shear zone in the footwall differs significantly in the along-strike direction not only in thickness, which varied from 100 to 300m, but also in lithology and mineral vein development. These variations might reflect primarily differences in lithology; that is, the sandstone-dominant shear zone with a large amount of mineral veins precipitated in microcracks is relatively thick, whereas the shale-dominant shear zone with a small amount of veins and with textures indicating highly pressurized pore fluid, is thinner. By comparison with characteristics of a shallow OST (3-5 km), we conclude that the shallow OST has experienced repeated brittle failure with rapid slip and focused fluid flow whereas the deep OST has experienced both brittle and ductile deformation, followed by fluid flow of various styles, depending on the lithology.

Original languageEnglish
Pages (from-to)333-351
Number of pages19
JournalIsland Arc
Volume18
Issue number2
DOIs
Publication statusPublished - 2009 Jun 16

Keywords

  • Cathodoluminescence
  • Fluid flow
  • Illite crystallinity
  • Nobeoka Tectonic Line
  • Out-of-sequence thrust
  • Shimanto accretionary complex

ASJC Scopus subject areas

  • Geology

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